Researching the Mechanisms after Total Shoulder Arthroplasty

Anna-Maria and Stephen Kellen Physician-Scientist Career Development Award Program – Part I

Researching the Mechanisms after Total Shoulder Arthroplasty:

We will post a series of blogs which will discuss specific research projects that are being conducted in part to the Anna-Maria and Stephen Kellen Physician-Scientist Career Development Award Program. In our first installment, Dr. Lawrence Gulotta discusses his research on the mechanisms after a total shoulder arthroplasty.

As a shoulder surgeon, I treat many patients with arthritis. While many of these patients can be treated with anti-inflammatories, cortisone injections and physical therapy, at times the arthritis becomes so bad that the only treatment left is a shoulder replacement. Shoulder replacement can be an excellent surgery to alleviate pain and improve function for an arthritic shoulder. It has changed the lives of countless numbers of patients. As with any orthopedic implant, there are still concerns about the longevity of the implants.

At HSS, approximately 95% of patients who undergo a shoulder replacement are satisfied with their shoulder at two years. With time, the metal and plastic that we use to replace the shoulder can loosen. Studies are shown that this happens at a rate of approximately 1% per year. That is, the risk of implant loosening is cumulative over time. Extrapolating these results out, one can assume that in 20 years, there will be approximately a 20% chance of having a loose part in the shoulder replacement. This can lead to pain and dysfunction, and often a second surgery to revise the implants. Determining ways to minimize this risk and to improve implant longevity has been the main focus of my research.

In 2012, I was fortunate enough to receive the Kellen Physician-Scientist Center Development Award in order to study the mechanisms of shoulder replacement loosening. The main focus of this research is to identify the forces that are transmitted across the socket portion of the joint under different scenarios. This understanding will lead to techniques and implants that improve the fixation in order to counterbalance these forces. We have concentrated on looking at the socket side of the replacement because that is the implant that is most likely to loosen over time.

Unlike the hip, the shoulder socket, also known in medical terms as the glenoid, is very small so there is not much bone to work with. Traditionally, the glenoid implant is made out of plastic and this implant is cemented into the bone. Various factors such as rotator cuff dysfunction, bony wear and overall implant deterioration can cause subsequent loosening of the implant out of the bone. When this occurs, it can cause pain and dysfunction for the patient and often requires revision surgery to replace the loose part. We are currently investigating ways to augment glenoid implant fixation into bone using screws. We are also investigating the effects of changing the angle at which the implant in placed, to see if this can help minimize the forces across the implant.

The Kellen Physician-Scientist Career Development Award has supplied me with the resources necessary to answer these questions. I now employ a full time research assistant who is able to oversee the day-to-day execution of our research studies. It has also allowed me time away from my clinical duties in order to concentrate on my research. I am very grateful for the generosity of both Marina Kellen French as well as the hospital which has all been integral in allowing my research efforts to continue. I am confident that with continued support, we will improve shoulder replacements to the point that revisions for implant loosening will be greatly minimized.

For more on the Anna-Maria and Stephen Kellen Physician-Scientist Career Development Award Program, check out the latest issue of Discovery to Recovery coming out in April 2014! Also stay tuned for part two in the HSS on the Move blog Series.

Dr. Lawrence Gulotta is an Orthopedic Surgeon at Hospital for Special Surgery, specializing in shoulder surgery and sports medicine. Dr. Gulotta’s interests include arthroscopic and open surgery, as well as non-operative management of shoulder problems. He currently serves as a reviewer for the Journal of Bone and Joint Surgery, the Journal of Shoulder and Elbow Surgery, Clinical Orthopaedics and Related Research, and the Journal of Orthopaedic Research. He is also on the Editorial Board of the HSS Journal.

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